In optical tape storage technology, precise tracking performance is typically required to position a laser in a tape drive relative to an optical tape so that the laser can read data from or write data to a proper track position on the tape. To assist in positioning of the laser, a servo pattern that encodes position information may be written onto the optical tape during manufacturing of the optical tape. The tape head may read the servo pattern, and a controller for the tape head may use a position signal decoded from the servo pattern to adjust the position of the tape head to move between tracks and/or follow a given track.
Servo patterns borrowed from conventional optical disk storage use an alternating land-and-groove pattern to demarcate individual data tracks in the tapes. Each data track may be written to a given land and uniquely identified by a periodic wobble in the corresponding land. To move from one data track to another, the tape drive may move the laser by an estimate of the distance separating the data tracks. The laser may then decode the wobble at the laser's new position to determine if the track currently read by the laser is the correct one. If the track is not the correct, target data track, the process may repeat until the right track is found. Consequently, servo tracking systems for optical tape drives may use potentially frequent, repetitive, and costly error recovery techniques to locate and identify the correct track during reading and/or writing of optical tapes.
The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.